Continuously variable transmission fluids comprising a combination of calcium-and magnesium-overbased detergents

ABSTRACT

A composition suitable for use as a lubricant for a transmission includes an oil of lubricating viscosity; a dispersant; a calcium detegent; a magnesium detergent; and an inorganic phosphorus compound. At least one of the dispersant or detergent components is borated.

BACKGROUND OF THE INVENTION

The present invention relates to formulations suitable for use as fluidsfor transmissions, especially continuously variable transmissions.Continuously variable transmissions (CVT) represent a radical departurefrom conventional automatic transmissions. The push belt version of theCVT was invented by Dr. Hub Van Doorne, and since its introduction, manycars have been equipped with the push belt CVT system. CVT push beltsare manufactured by Van Doorne's Transmissie VB of Tilburg, theNetherlands. A more detailed description of such transmissions and beltsand lubricants employed therein is found in European Patent Application753 564, published Jan. 15, 1997, as well as references cited therein.In brief, a belt and pulley system is central to the operation of thistype of transmission. The pulley system comprises a pair of pulleys witha V-shaped cross-section, each consisting of a moveable sheave, a fixedsheave, and a hydraulic cylinder. Between the pulleys runs a belt, whichconsists of a set of metal elements held together by metal bands. Inoperation, the driving pulley pushes the belt to the driven pulley,thereby transferring power from the input to the output. Thetransmission drive ratio is controlled by opening or closing themoveable sheaves so that the belt rides lower or higher on the pulleyfaces. This manner of operation permits continuous adjustment of gearratio between the input and output shafts.

It has become clear from commercial use of the CVT that the fluids usedin the CVT are just as important as the mechanical design forsatisfactory operation. The lubricant must fulfill several functions: tolubricate the metal belt in its contacts with the pulley assembly, theplanetary and other gears, the wet-plate clutches, and the bearings; tocool the transmission; and to carry hydraulic signals and power. Thehydraulic pressure controls the belt traction, transmission ratio, andclutch engagement. The lubricant must provide the appropriate degree offriction between the belt and pulley assembly, to avoid the problem ofslippage on one hand, and binding on the other, all the while providingprotection to the metal surfaces from pitting, scuffing, scratching,flaking, polishing, and other forms of wear. Accordingly, the fluidshould maintain a relatively high coefficient of friction formetal/metal contact, as well as exhibiting a suitable degree of shearstability.

PCT Patent Application WO 00/70001, November, 2000, disclosesformulations suitable for use as fluids for continuously variabletransmissions, comprising (a) an oil of lubricating viscosity; and (b) adispersant; or (c) a detergent; or mixtures of (b) and (c), wherein atleast one of the dispersant (b) and the detergent (c) is a boratedspecies and wherein the amount of boron supplied to the formulation issufficient to impart improved friction and anti-seizure properties tosaid formulation.

U.S. Pat. No. 5,759,965, Sumiejski, Jun. 2, 1998, discloses antiwearenhancing composition for lubricants and functional fluids. It includesa boron-containing overbased material, a phosphorus acid, ester, orderivative, and a borated epoxide or borated fatty acid ester, andoptionally a thiocarbamate.

The metal-metal coefficient of friction and the antiseizure propertiesof CVT fluids are important performance parameters for the effectiveapplication of continuously variable transmissions. The presentinvention solves the problem of providing a suitable CVT fluid withexceptional metal-metal friction and good antiseizure properties. Theformulations exhibit both a high dynamic coefficient of friction (metalon metal) and a positive slope in the plot of dynamic friction versussliding speed.

The compositions of the present invention can also be used aslubricating oils and greases useful in other industrial applications andin automotive engines, transmissions and axles. These compositions areeffective in a variety of applications including crankcase lubricatingoils for spark-ignited and compression-ignited internal combustionengines, including automobile and truck engines, two-cycle engines,aviation piston engines, marine and low-load diesel engines, and thelike. They are also useful as additives for traction fluids. Also,automatic transmission fluids, manual transmission fluids, transaxlelubricants, gear lubricants, metalworking lubricants, hydraulic fluids,and other lubricating oil and grease compositions can benefit from theincorporation of the compositions of this invention. The inventivefunctional fluids are particularly effective as automatic transmissionfluids, particularly fluids for continuously variable transmissions,including push-belt type and toroidal traction drive transmissions, aswell as dual clutch transmissions.

SUMMARY OF THE INVENTION

The present invention provides a composition suitable for use as alubricant for a transmission, comprising:

-   -   (a) an oil of lubricating viscosity;    -   (b) a dispersant;    -   (c) calcium detergent;    -   (d) a magnesium detergent; and    -   (e) an inorganic phosphorus compound;    -   wherein at least one of (b), (c), and (d) is borated.

The present invention further provides a method for lubricating atransmission, comprising imparting to said transmission theaforedescribed formulation.

DETAILED DESCRIPTION OF THE INVENTION

Various preferred features and embodiments will be described below byway of non-limiting illustration.

The first component of the present invention is (a) an oil oflubricating viscosity which is generally present in a major amount (i.e.an amount greater than 50% by weight). Generally, the oil of lubricatingviscosity is present in an amount of greater than 80% by weight of thecomposition, typically at least 85%, preferably 90 to 95%. Such oil canbe derived from a variety of sources, and includes natural and syntheticlubricating oils and mixtures thereof.

The natural oils useful in making the inventive lubricants andfunctional fluids include animal oils and vegetable oils (e.g., lardoil, castor oil) as well as mineral lubricating oils such as liquidpetroleum oils and solvent treated or acid-treated mineral lubricatingoils of the paraffinic, naphthenic or mixed paraffinic/naphthenic typeswhich may be further refined by hydrocracking and hydrofinishingprocesses and are dewaxed. Oils of lubricating viscosity derived fromcoal or shale are also useful. Useful natural base oils may be thosedesignated by the American Petroleum Institute (API) as Group I, II, orIII oils. Group I oils contain <90% saturates and/or >0.03% sulfur andhave a viscosity index (VI) of ≧80. Group II oils contain ≧90%saturates, ≦0.03% sulfur, and have a VI≧80. Group III oils are similarto group II but have a VI≧120.

Upon occasion, highly refined or hydrocracked natural oils have beenreferred to as “synthetic” oils. More commonly, however, syntheticlubricating oils are understood to include hydrocarbon oils andhalo-substituted hydrocarbon oils such as polymerized andinterpolymerized olefins (e.g., polybutylenes, polypropylenes,propylene-isobutylene copolymers, chlorinated polybutylenes);poly(1-hexenes), poly(1-octenes), poly(1-decenes), and mixtures thereof;alkyl-benzenes (e.g., dodecylbenzenes, tetradecylbenzenes,dinonylbenzenes, di-(2-ethylhexyl)-benzenes); polyphenyls (e.g.,biphenyls, terphenyls, alkylated polyphenyls); alkylated diphenyl ethersand alkylated diphenyl sulfides and the derivatives, analogs andhomologs thereof and the like. Polyalpha olefin oils are also referredto as API Group IV oils.

In one embodiment, the oil of lubricating viscosity is apoly-alpha-olefin (PAO). Typically, the poly-alpha-olefins are derivedfrom monomers having from 4 to 30, or from 4 to 20, or from 6 to 16carbon atoms. Examples of useful PAOs include those derived from1-decene. These PAOs may have a viscosity from 2 to 150.

Preferred base oils include poly-α-olefins such as oligomers of1-decene. These synthetic base oils are hydrogenated resulting in an oilof stability against oxidation. The synthetic oils may encompass asingle viscosity range or a mixture of high viscosity and low viscosityrange oils so long as the mixture results in a viscosity which isconsistent with the requirements set forth below. Also included aspreferred base oils are highly hydrocracked and dewaxed oils. Thesepetroleum oils are generally refined to give enhanced low temperatureviscosity and antioxidation performance. Mixtures of synthetic oils withrefined mineral oils may also be employed.

Another class of oils is known as traction oils, which are typicallysynthetic fluids containing a large fraction of highly branched orcycloaliphatic structures, i.e., cyclohexyl rings. Traction oils ortraction fluids are described in detail, for example, in U.S. Pat. Nos.3,411,369 and 4,704,490.

Other suitable oils can be oils derived from a Fischer-Tropsch processand hydrogenation.

(b) Another component of the present invention is a dispersant,preferably a borated dispersant. Dispersants which can be used in thepresent invention, and borated if desired, include succinimidedispersants, ester dispersants, ester-amide dispersants, Mannichdispersants, alkyl amino phenol dispersants, polyalkene-acrylic aciddispersant, polyether dispersants, and condensation products of fattyhydrocarbyl monocarboxylic acylating agents with an amine or ammonia.Dispersants of these and other types are well known in the technology oflubricant additives. Besides boration, such dispersants can also bepost-treated by reaction with any one or more of a variety of agents.Among these are urea, thiourea, dimercaptothiadiazoles, carbondisulfide, aldehydes, ketones, carboxylic acids, hydrocarbon-substitutedsuccinic anhydrides, nitriles, epoxides, and phosphorus compounds. Thus,the dispersant can also be a phosphorylated borated dispersant.References detailing such treatment are listed in U.S. Pat. No.4,654,403.

Succinimide dispersants include reaction products of one or morehydrocarbyl-substituted succinic acids, anhydride, or reactiveequivalents thereof, with one or more amines. Succinimide dispersantshave a variety of chemical structures including typically

where each R¹ is independently an alkyl group, frequently a polyisobutylgroup with a molecular weight of 500-5000, optionally substituted withmultiple succinic groups. R² are alkylenel groups, commonly ethylene(C₂H₄) groups. Such molecules are commonly derived from reaction of analkenyl acylating agent with a polyamine, and a wide variety of linkagesbetween the two moieties is possible beside the simple imide structureshown above, including a variety of amides and quaternary ammoniumsalts. The structure will, of course, also vary as the type of polyaminevaries. Succinimide dispersants are more fully described in U.S. Pat.Nos. 4,234,435 and 3,172,892.

The polyamine which reacts with the succinic acylating agent can bealiphatic, cycloaliphatic, heterocyclic or aromatic. Examples of thepolyamines include alkylene polyamines, hydroxy containing polyamines,arylpolyamines, and heterocyclic polyamines.

Alkylene polyamines are represented by the formula

wherein n typically has an average value from 1 to 4 or 6 to and the“Alkylene” group typically has from 1 to 10 carbon atoms. Each R₅ isindependently hydrogen, or an aliphatic or hydroxy-substituted aliphaticgroup of up to 30 carbon atoms.

Such alkylenepolyamines include methylenepolyamines, ethylenepolyamines,butylenepolyamines, propylenepolyamines, pentylenepolyamines, etc. Thehigher homologs and related heterocyclic amines such as piperazines andN-aminoalkyl-substituted piperazines are also included. Specificexamples of such polyamines are ethylenediamine, diethylenetriamine(DETA), triethylenetetramine (TETA), tris-(2-aminoethyl)amine,propylenediamine, trimethylenediamine, tripropylenetetramine,tetraethylenepentamine, hexaethyleneheptamine, andpentaethylenehexamine. Ethylenepolyamines and their preparation aredescribed in detail under the heading Ethylene Amines in Kirk Othmer's“Encyclopedia of Chemical Technology”, 2d Edition, Vol. 7, pages 22-37,Interscience Publishers, New York (1965).

Other useful types of polyamine mixtures are those resulting fromstripping of the above-described polyamine mixtures to leave as residuewhat is often termed “polyamine bottoms”. Another useful polyamine is acondensation reaction between at least one hydroxy compound with atleast one polyamine reactant containing at least one primary orsecondary amino group. The hydroxy compounds are preferably polyhydricalcohols and amines. The amine condensates and methods of making thesame are described in U.S. Pat. No. 5,053,152.

In another embodiment, the polyamines are hydroxy-containing polyamines;in another embodiment, the amine is a heterocyclic polyamine.

The reaction products of hydrocarbyl-substituted succinic acylatingagents and amines and methods for preparing the same are described inU.S. Pat. Nos. 4,234,435; 4,952,328; 4,938,881; 4,957,649; and4,904,401.

Ester dispersants are similar to the succinimide dispersants, describedabove, except that they may be seen as having been prepared by reactionof a hydrocarbyl acylating agent (such as a hydrocarbyl succinicanhydride) and a polyhydric aliphatic alcohol such as glycerol,pentaerythritol, or sorbitol. Such materials are described in moredetail in U.S. Pat. No. 3,381,022. Likewise, esteramide dispersants aresimilar to succinimide dispersants except that they can be prepared fromamino alcohols or mixtures of amines an alcohols such that the productwill contain both ester and amide functionality.

Another class of dispersant is Mannich dispersants, also known asMannich bases. These are materials which are formed by the condensationof a higher molecular weight, alkyl substituted phenol, an alkylenepolyamine, and an aldehyde such as formaldehyde. Such materials may havethe general structure

(including a variety of isomers and the like) and are described in moredetail in U.S. Pat. No. 3,634,515.

Other dispersants include polymeric dispersant additives, which aregenerally hydrocarbon-based polymers which contain polar functionalityto impart dispersancy characteristics to the polymer. The polarfunctionality can be in the form of amino functionality. The polymer- orhydrocarbyl-substituted amines can be formed by heating a mixture of achlorinated olefin or polyolefin such as a chlorinated polyisobutylenewith an amine such as ethylenediamine in the presence of a base such assodium carbonate as described in U.S. Pat. No. 5,407,453. Similarly,other functionality can be imparted, such as carboxylic acidfunctionality (by reaction with an acid such as acrylic acid.) If thehydrocarbon-based polymer is of a suitable molecular weight to be aviscosity modifier, the resulting material can be referred to as adispersant viscosity modifier.

The dispersant can also be a condensation product of a fatty hydrocarbylmonocarboxylic acylating agent, such as a fatty acid, with an amine orammonia. The hydrocarbyl portion of the fatty hydrocarbyl monocarboxylicacylating agent can be an aliphatic group, which can be linear orbranched, saturated, unsaturated, or a mixture thereof. The aliphaticgroup can have 1 to 50 carbon atoms, preferably 8, 10, or 12 to 20carbon atoms. The acylating agent can be an aliphatic carboxylic acidcomprising a carboxy group (COOH) and an aliphatic group. Themonocarboxylic acylating agent can be a monocarboxylic acid or areactive equivalent thereof, such as an anhydride, an ester, or an acidhalide such as stearoyl chloride. Useful monocarboxylic acylating agentsare available commercially from numerous suppliers and include tall oilfatty acids, oleic acid, stearic acid and isostearic acid. Fatty acidscontaining 12 to 24 carbon atoms, including C18 acids, are particularlyuseful. The amine can be any of the amines described above.

Alkyl amino phenol dispersants are hydrocarbyl-substituted aminophenols.The hydrocarbyl substituent of the aminophenol can have 10 to 400 carbonatoms. The hydrocarbyl substituent can be derived from an olefin or apolyolefin, as described above in connection with the Mannichdispersant. The hydrocarbyl-substituted aminophenol can have one or moreamino groups. The hydrocarbyl-substituted aminophenol can be prepared byalkylating phenol with an olefin or a polyolefin, nitrating thealkylated phenol with a nitrating agent such as nitric acid, andreducing the nitrated phenol with a reducing agent as described in U.S.Pat. No. 4,724,091.

Polyether dispersants include polyetheramines, polyether amides,polyether carbamates, and polyether alcohols. Polyetheramines can berepresented by the formula R[OCH₂CH(R¹)]_(n)A, where R is a hydrocarbylgroup, R¹ is hydrogen or a hydrocarbyl group of 1 to 16 carbon atoms, ormixtures thereof, n is 2 to 50, and A can be —OCH₂CH₂CH₂NR²R² or —NR³R³,where each R² is independently hydrogen or hydrocarbyl and each R³ isindependently hydrogen, hydrocarbyl, or an alkyleneamine group.Polyetheramines and their methods of preparation are described ingreater detail in U.S. Pat. No. 6,458,172, columns 4 and 5. Polyetheralcohols include hydrocarbyl-terminated poly(oxyalkylene) monools,including the hydrocarbyl-terminated poly(oxypropylene) monoolsdescribed in greater detail in U.S. Pat. No. 6,348,075; see inparticular column 8. The hydrocarbyl group can be an alkyl oralkyl-substituted aromatic group of 8 to 20 carbon atoms, such as C₁₂₋₁₆alkyl or nonylphenyl.

The dispersant is, in one embodiment, a borated dispersant. Typically,the borated dispersant contains from 0.1% to 5%, or from 0.5% to 4%, orfrom 0.7% to 3% by weight boron. Borated dispersants are described inU.S. Pat. Nos. 3,000,916; 3,087,936; 3,254,025; 3,282,955; 3,313,727;3,491,025; 3,533,945; 3,666,662, 4,925,983 and 5,883,057. They areprepared by reaction of one or more dispersants with one or more boroncompounds.

Suitable boron compounds for preparing borated dispersants includevarious forms of boric acid (including metaboric acid, HBO₂, orthoboricacid, H₃BO₃, and tetraboric acid, H₂B₄O₇), boric oxide, boron trioxide,and alkyl borates of the formula (RO)_(x)B(OH)_(y) wherein x is 1 to 3and y is 0 to 2, the sum of x and y being 3, and where R is an alkylgroup containing 1 to 6 carbon atoms. In one embodiment, the boroncompound is an alkali or mixed alkali metal and alkaline earth metalborate. These metal borates are generally hydrated particulate metalborates which are known in the art. Alkali metal borates include mixedalkali and alkaline metal borates. These metal borates are availablecommercially.

The dispersant can also be a mixture of one or more borated dispersantswith one or more non-borated dispersants.

The amount of the dispersant, on an oil free basis, in the fullyformulated fluids of the present invention can be 0.5 to 6 percent byweight, preferably 1 to 4 or 2 to 3 percent by weight. The dispersantcan contribute 50 to 3000 parts per million (ppm) boron, preferably 80to 1500 ppm, and more preferably 150, 200, 250, or 500 ppm to 1200 ppmboron, to the fully formulated fluid.

Another required component of the present invention is a combination oftwo detergents (c) a calcium detergent and (d) a magnesium detergent,which are typically in the form of overbased metal salts. Overbasedmaterials are generally single phase, homogeneous Newtonian systemscharacterized by a metal content in excess of that which would bepresent for neutralization according to the stoichiometry of the metaland the particular acidic organic compound reacted with the metal. Theoverbased materials are most commonly prepared by reacting an acidicmaterial (typically an inorganic acid or lower carboxylic acid,preferably carbon dioxide) with a mixture comprising an acidic organiccompound, a reaction medium comprising at least one inert, organicsolvent (such as mineral oil, naphtha, toluene, or xylene) for saidacidic organic material, a stoichiometric excess of a metal base, and apromoter such as a phenol or alcohol. The detergent components of thepresent additive mixture can be one or more borated or non-boratedoverbased salts of a sulfonic acid, phenol, salicylic acid, glyoxylicacid, carboxylic acid, or phosphorus-containing acid, or mixturesthereof. The term “salicylate” is used herein, as commonly in the art,to preferably mean salts of hydrocarbyl-substituted salicylic acid.

Sulfonate salts, which are among those preferred, are those having asubstantially oleophilic character and which are formed from organicmaterials. Organic sulfonates are well known materials in the lubricantand detergent arts. The sulfonate compound should contain on average 10to 40 carbon atoms, preferably 12 to 36 and more preferably 14 to 32carbon atoms. While the carbon atoms can be either in an aromatic orparaffinic configuration, it is preferred that alkylated aromatics beused. While naphthalene based materials can be used, the preferredaromatic materials are based on benzene.

A preferred composition includes an overbasedhydrocarbylbenzenesulfonate, typically an alkyl sulfonate, such as amonosulfonated alkylated benzene, preferably the monoalkylated benzene.Typically, alkyl benzene fractions are obtained from still bottomsources and are mono- or di-alkylated. A mixture of mono-alkylatedaromatics can be used to obtain the mono-alkylated salt (benzenesulfonate). Mixtures in which a substantial portion of the compositioncontains polymers of propylene as the source of the alkyl groups assistin the solubility of the salt in the transmission fluids of the presentinvention.

In one embodiment, the overbased calcium detergent can be an overbasedcalcium hydrocarbylsalicylate. In one embodiment the overbased magnesiumdetergent can be an overbased magnesium hydrocarbylphenate.

The detergent is typically overbased. By overbasing, it is meant that astoichiometric excess of the metal be present, beyond that required toneutralize the anion of the salt. The excess metal from overbasing hasthe effect of neutralizing acids which may build up in the lubricant.The overbasing is generally done such that the metal ratio is at least1.05:1 or 1.1:1, preferably 2:1 to 30:1, and most preferably 4:1 to25:1. The metal ratio is the ratio of metal ions, on an equivalentbasis, to the anionic portion (i.e, the sulfonate, phenate, salicylateor other such materials as described above) of the overbased material.The above-identified metal ratios can apply to both the calciumdetergent and the magnesium detergent.

Preferably the overbased materials are carbonated materials. Carbonatedoverbased materials are those which the low molecular weight acidicmaterial which is preferably used in the formation of the material iscarbon dioxide. The preparation of overbased materials, includingcarbonated overbased materials, is well known and is described, innumerous United States patents including, for example, U.S. Pat. No.3,766,067, McMillen.

The overbased materials can be borated or non-borated, as describedbelow. The overbased materials (detergents) can also be a mixture of oneor more borated detergents with one or more non-borated detergents.Borated overbased materials and their preparation are well known and aredescribed in greater detail in European Patent Application 753,564,published Jan. 15, 1997 and in U.S. Pat. No. 4,792,410. In a preferredembodiment, the magnesium detergent is a borated magnesium sulfonatedetergent.

Boronating agents include those described above in reference to theborated dispersants. An alkali metal borate dispersion can be preparedby the following steps: a suitable reaction vessel is charged with analkaline metal carbonate overbased metal sulfonate within an oleophilicreaction medium (typically the hydrocarbon medium employed to preparethe overbased metal sulfonate). Boric acid is then charged to thereaction vessel and the contents vigorously agitated. The reaction istypically conducted for a period of 0.5 to 7 hours, usually from 1 to 3hours at a reaction temperature of 20° C. to 200° C., preferably from20° C. to 150° C., and more preferably from 40° C. to 125° C. At the endof the reaction period, the temperature is typically raised to 100° C.to 250° C., preferably from 100° C. to 150° C. to strip the medium ofany residual alcohol and water. The stripping can be done at atmospherepressure or under reduced pressure of, e.g., 93 kPa to 1 kPa.

The detergent, when it is borated, will preferably contribute 50 to 3000parts per million (ppm) boron, more preferably 80 to 1500 ppm, and stillmore preferably 150, 200, 250, or 500 ppm to 1200 ppm boron, to thefully formulated fluid.

The amount of the calcium detergent can be 0.025 to 6 percent by weight,or 0.05 to 2 percent or to 1 percent by weight, or 0.1 to 1 percent byweight, or 0.1 to 0.4 percent by weight. The amount of the magnesiumdetergent can be 0.025 to 6 percent by weight, or 0.05 to 2 percent orto 1 percent by weight, or 0.1 to 1 percent by weight, or 0.1 to 0.4percent by weight.

The amount of the borated additives, whether dispersants, detergents, orboth, is preferably an amount suitable to provide friction andantiseizure properties similar to those achieved by the use ofconventional zinc dialkyldithiophosphates. The preferred total amount ofboron present in the fully formulated composition is at least 130 or 200ppm, preferably at least 250 ppm, more preferably 400, to 3300 or to2000 ppm, and even more preferably 600 or 700 ppm to 1700 or 1300 ppm.

The composition of the present invention also contains (e) an inorganicphosphorus compound, typically in an amount of 0.005 to 0.3 percent byweight, preferably 0.02 or 0.03 or 0.04 percent to 0.2 or 0.16 or 0.13percent (e.g., 0.02 to 0.2 percent by weight).

The inorganic phosphorus compound may contain an oxygen atom and/or asulfur atom as its constituent elements, and includes the followingsexamples: phosphorous acid, phosphoric acid, polyphosphoric acid,hypophosphoric acid, phosphorus trioxide, phosphorus tetroxide,phosphorous pentoxide, phosphorotetrathionic acid (H₃PS₄),phosphoromonothionic acid (H₃PO₃S), phosphorodithionic acid (H₃PO₂S₂),phosphorotrithionic acid (H₃PO₂S₃), and P₂S₅. Among these, phosphorousacid and phosphoric acid are preferred. A salt, such as an amine salt ofan inorganic phosphorus compound can also be used. It is also possibleto use a plurality of these inorganic phosphorus compounds together. Theinorganic phosphorus compound is preferably phosphoric acid orphosphorous aicd, preferably phosphoric acid, which is conventionallysupplied as 85% aqueous phosphoric acid (i.e., 85% phosphoric acid(aqueous), the remaining 15% being water), for which the amount ofphosphoric acid can be readily calculated. If the magnesium detergent(d) or the calcium detergent (c) is a borated species, relatively lowerlevels of the phosphorus acid (or other inorganic phosphorus compound)can be used (0.02 to 0.08 or 0.1 percent); otherwise, relatively higherlevels can be preferred (0.08 or 0.1 to 0.2 percent).

The compositions of the present invention will generally contain otheradditives commonly used for ATFs or fluids for CVTs.

One common component for ATFs or CVT fluids is a viscosity modifier,(“VM,” also referred to as a viscosity index improver). Viscositymodifiers are extremely well known in the art and most are commerciallyavailable. Hydrocarbon VMs include polybutenes, poly(ethylene/propylene)copolymers, and copolymers of styrene with butadiene or isoprene. EsterVMs include esters of styrene/maleic anhydride polymers, esters ofstyrene/maleic anhydride/acrylate terpolymers, and polymethacrylates.The acrylates are available from RobMax and from The LubrizolCorporation, polybutenes from Ethyl Corporation and Lubrizol,ethylene/propylene copolymers from Exxon and Texaco,polystyrene/isoprene polymers from Shell, styrene/maleic esters fromLubrizol, and styrene/butadiene polymers from BASF.

The viscosity modifier can also be a dispersant viscosity modifier,prepared by reacting, in the presence of a free radical initiator,

-   -   55% to 99.9% by weight of an alkyl acrylate ester monomers        containing 1 to 24 carbon atoms in the ester alkyl group,        wherein at least 50 mole % of the esters contain at least 6        carbon atoms, preferably at least 8 carbon atoms, in the ester        alkyl group, and    -   0.1% to 45% by weight, and in one embodiment 1.5 to 8% by weight        of at least one nitrogen-containing monomer selected from the        group consisting of vinyl substituted nitrogen heterocyclic        monomers, dialkylaminoalkyl acrylate monomers, dialkylaminoalkyl        acrylamide monomers, N-tertiary alkyl acrylamides, and vinyl        substituted amines.

In one embodiment the dispersant viscosity modifier is prepared bypolymerizing 57.5 parts methyl methacrylate, 12.7 parts butylmethacrylate, 226.5 parts each of C₉₋₁₁ methacrylate and C₁₂₋₁₅methacrylate, 114.8 parts C₁₆₋₁₈ methacrylate and 11.7 partsN-(3-(dimethylamino)propyl) methacrylamide in a staged addition process.Details of the preparation of these and related polymers are found inEuropean Patent Application 750,031, published Dec. 27, 1996.

The copolymers described above typically have a weight average molecularweight ({overscore (M)}_(w)) of 10,000 to 500,000, more often 30,000 to250,000, frequently 20,000 to 100,000 and polydispersity values({overscore (M)}_(w)/{overscore (M)}_(n)) of 1.2 to 5. Molecular weightsof polymers are determined using well-known methods described in theliterature.

Normally the amount of VM will be 1 to 25 percent by weight of thecomposition; preferably the amount will be 2 to 20 percent by weight,and more preferably 5 to 15 percent by weight.

Another common component for ATFs and CVT fluids is a phosphoruscompound (other than inorganic phosphorus compound such as phosphoricacid, already described above), preferably (f) an organic phosphorusester, amide, or amine salt. Most such phosphorus compounds impart ameasure of anti-wear performance to the composition.

The phosphorus compound can be a phosphorus ester of the formula(R¹X)(R²X)P(X)_(n)X_(m)R³ or a salt thereof, where each X isindependently an oxygen atom or a sulfur atom, n is 0 or 1, m is 0 or 1,m+n is 1 or 2, and R¹, R², and R³ are hydrogen or hydrocarbyl groups. Atleast one of R¹, R², and R³ is a hydrocarbyl group, and preferably atleast one is hydrogen. This component thus includes phosphite esters,phosphate esters, and thiophosphite and thiophosphate esters. The esterscan be mono-, di- or tri-hydrocarbyl esters. It is noted that certain ofthese materials can exist in tautomeric forms, and that all suchtautomers are intended to be encompassed by the above formula andincluded within the present invention. For example certain phosphiteesters can be written in at least two ways, (RO)₂—PH(═O) and (RO)₂—P—OH,differing merely by the placement of the hydrogen. Each of thesestructures are intended to be encompassed by the present invention.

The total number of carbon atoms in R¹, R² and R³ in each of the aboveformula (for the phosphorus compound) should be sufficient to render thecompound soluble in the medium. Generally, the total number of carbonatoms in R¹, R² and R³ is at least 8, and in one embodiment at least 12,and in one embodiment at least 16. There is no limit to the total numberof carbon atoms in R¹, R² and R³ that is required, but a practical upperlimit is 400 or 500 carbon atoms. In one embodiment, R¹, R² and R³ inthe above formula are independently hydrocarbyl groups of preferably 1to 100 carbon atoms, or 1 to 50 carbon atoms, or 1 to 30 carbon atoms.Each R¹, R² and R³ can be the same as the other, although they may bedifferent. Examples of useful R¹, R² and R³ groups include hydrogen,t-butyl, isobutyl, amyl, isooctyl, decyl, dodecyl, oleyl, C₁₈ alkyl,eicosyl, 2-pentenyl, dodecenyl, phenyl, naphthyl, alkylphenyl,alkylnaphthyl, phenylalkyl, naphthylalkyl, alkylphenylalkyl, andalkylnaphthylalkyl.

It is preferred that at least two of the X atoms in the above structureare oxygen, so that the structure will be (R¹O)(R²O)P(X)_(n)X_(m)R³, andmore preferably (R¹O)(R²O)P(X)_(n)X_(m)H.

The R¹ and R² groups can comprise a mixture of hydrocarbyl groupsderived from commercial alcohols. Examples of some preferred monohydricalcohols and alcohol mixtures include the commercially available Alfol™alcohols marketed by Continental Oil Corporation. Alfol™ 810, forinstance, is a mixture containing alcohols consisting essentially ofstraight-chain primary alcohols having from 8 to 10 carbon atoms.Another commercially available alcohol mixture is Adol™ 60 whichcomprises about 75% by weight of a straight-chain C₂₂ primary alcohol,about 15% of a C₂₀ primary alcohol, and about 8% of C₁₈ and C₂₄alcohols. The Adol™ alcohols are marketed by Ashland Chemical.

A variety of mixtures of monohydric fatty alcohols derived fromnaturally occurring triglycerides and ranging in chain length from C₈ toC₁₈ are available from Procter & Gamble Company. Another group ofcommercially available mixtures include the Neodol™ products availablefrom Shell Chemical Co. Other alcohols which can be used are lowermolecular weight alcohols such as methanol, ethanol, propanol,isopropanol, normal butanol, isobutanol, tertbutanol, the pentanols,hexanols, heptanols, octanols (including 2-ethyl hexanol), nonanols,decanols, and mixtures thereof.

The dihydrocarbyl hydrogen phosphites, such as dibutyl hydrogenphosphite, useful in this invention can be prepared by techniques wellknown in the art, and many such phosphites are available commercially.

In one embodiment, the phosphorus-containing agent is a hydrocarbylphosphate. In another embodiment, the hydrocarbyl phosphate can be ahydrocarbyl thiophosphate. In yet another embodiment, the phosphoruscompound can be a phosphorus-containing amide. Phosphorus-containingamides are generally prepared by reacting one of the above-describedphosphorus acids such as a phosphoric, phosphonic, phosphinic,thiophosphoric, including dithiophosphoric as well asmonothiophosphoric, thiophosphinic or thiophosphonic acids with anunsaturated amide, such as an acrylamide.

Examples of phosphorus-containing materials are phosphites andphosphates such as dibutyl phosphite, diphenylphosphite,triphenylphosphite, tricresylphosphate and triphenylthiophosphate.

The amount of the phosphorus containing compound or compounds(especially the organic phosphorus ester (f)) in the fully formulatedfluids of the present invention (other than the inorganic phosphoruscompound of (e)), will typically be 0.01 to 6 percent by weight or 0.02to 2 percent or 0.03 to 1 percent, or 0.04 to 0.5 percent by weight.Alternative amounts include 0.05 to 5 percent by weight, preferably 0.1to 2 percent, and more preferably 0.2 to 1 percent by weight. The amountof such compounds will depend to some extent on the specific compound,its molecular weight, phosphorus content, and activity. Thus, the amountof the organic phosphorus ester (f) can also be described as an amountsufficient to contribute 0.005 to 2 percent phosphorus to thecomposition, preferably 0.006 to 1 percent P or 0.007 to 0.5 or 0.1percent P. Typically the fully formulated fluids of the presentinvention will contain 150 to 1000 parts per million phosphorus,preferably 300 to 500 ppm phosphorus from all sources.

Another common component of ATFs and CVT fluids is one or more frictionmodifiers. Friction modifiers are very well known in the art, and thenumber and types of compounds are voluminous. In general, frictionmodifiers include metal salts of fatty acids, fatty phosphites, fattyacid amides, fatty epoxides and borated derivatives thereof, fattyamines, glycerol esters and their borated derivatives, alkoxylated fattyamines (including ethoxylated fatty amines such as diethoxylatedtallowamine) and their borated derivatives, isostearic acid condensationproducts of polyamines such as tetraethylene pentamine, such condensatescontaining amide and imidazoline or imine functional groups, (includingalso N-hydroxyethyl oleylimidazoline and low molecular weightalkenylsuccinimides), sulfurized olefins, sulfurized polyolefins,sulfurized fats, and sulfurized fatty acids. They can also be suspendedmolybdenum disulfide, dialkyl or diaryl dithiophosphate molybdates oralkyl or dialkyl dithiocarbamate molybdates where the molybdenum isoxydisulfidobridged and chelated with dithiophosphate or dithiocarbamateligands.

The amount of the friction modifier component, if present, can be 0.01to 2.5 percent by weight of the composition, preferably 0.025 to 1.00percent, more preferably 0.1 to 0.45 percent, 0.15 to 0.3 percent, or0.2 to 0.25 percent by weight. The total amount of the frictionmodifiers (of all types) is preferably that which provides ametal-to-metal coefficient of friction of at least 0.120 as measured at110° C. by ASTM-G-77, using the composition as a lubricant, since suchminimum friction is desirable for the presently contemplatedapplication. Preferably the amount of friction modifiers is sufficientto provide a coefficient of friction of 0.125 to 0.145 or 0.142, andmore preferably about 0.135.

Other materials often used in ATFs and CVT fluids include antioxidants,including hindered phenolic antioxidants, secondary aromatic amineantioxidants, sulfurized phenolic antioxidants, oil-soluble coppercompounds, phosphorus-containing antioxidants, organic sulfides,disulfides, and polysulfides. Other components include metaldeactivators such as tolyltriazole, benzotriazole, and themethylene-coupled product of tolyltriazole and amines such as2-ethylhexylamine. Such metal deactivators can also be useful inadjusting the metal-to-metal friction in push belt CVTs. Othercomponents can include seal swell compositions, such as isodecylsulfolane (that is, isodecyl-3-sulfolanyl ether), which are designed tokeep seals pliable. Also permissible are pour point depressants, such asalkylnaphthalenes, polymethacrylates, vinyl acetate/fumarate or /maleatecopolymers, and styrene/maleate copolymers. These optional materials areknown to those skilled in the art, are generally commercially available,and are described in greater detail in published European PatentApplication 761,805. Also included can be corrosion inhibitors, dyes,fluidizing agents, and antifoam agents. Each of these materials may bepresent in conventional and functional amounts.

The various components which can be used in the present invention aredescribed in greater detail in PCT Patent Application WO 00/70001.

The composition of the present invention can be supplied as a fullyformulated lubricant or functional fluid, or it can be supplied as aconcentrate. In a concentrate, the relative amounts of the variouscomponents will generally be about the same as in the fully formulatedcomposition, except that the amount of oil of lubricating viscosity willbe decreased by an appropriate amount. The absolute percentage amountsof the remaining components will be correspondingly increased. Thus,when the concentrate is added to an appropriate amount of oil, the finalformulation of the present invention will be obtained. A typicalconcentrate of the present invention may contain at least 2500 parts permillion of boron.

Thus, in a fully formulated composition, the amount of the oil oflubricating viscosity will typically be a major amount, or 50 to 95parts by weight. In a concentrate, similarly, the amount of the oil oflubricating viscosity will typically be 10 to 50 parts by weight or 10to 50 perent, or other intermediate values that may be appropriate.Other amounts of the various components may be independently selectedfrom a consideration of the broad, preferred, and most preferred percentranges of such components set forth above. In one embodiment, therelative weight ratios of components (b, the borated succinimidedispersant) to (c, the calcium detergent) to (d, the magnesiumdetergent) to (e, the phosphoric acid) are about (1 to 4) to (0.05 to 1)to (0.05 to 1) to (0.02 to 2).

In one preferred embodiment, the present invention provides acomposition suitable for use as a lubricant for a transmission,comprising:

-   -   (a) an oil of lubricating viscosity;    -   (b) 1 to 4 percent by weight of a borated succinimide        dispersant, said borated succinimide dispersant being the        reaction product of a polyisobutenylsuccinic anhydride with        polyethyleneamines, further reacted with boric acid; wherein        said borated succinimide dispersant contributes 50 to 3000 parts        per million by weight boron to the composition;    -   (c) 0.1 to 1 percent by weight of an overbased calcium        alkylbenzenesulfonate detergent having a metal ratio of about        4:1 to about 25:1;    -   (d) 0.1 to 1 percent by weight of an overbased magnesium        alkylbenzenesulfonate detergent having a metal ratio of 4:1 to        25:1;    -   (e) 0.01 to 0.2 percent by weight of phosphori acid as 85%        phosphoric acid (aqueous); and    -   (f) 0.2 to 2 percent by weight of a dialkyl hydrogen phosphite;    -   wherein said composition contains 130 to 3300 parts per million        by weight boron.

As used herein, the term “hydrocarbyl substituent” or “hydrocarbylgroup” is used in its ordinary sense, which is well-known to thoseskilled in the art. Specifically, it refers to a group having a carbonatom directly attached to the remainder of the molecule and havingpredominantly hydrocarbon character. Examples of hydrocarbyl groupsinclude:

-   -   hydrocarbon substituents, that is, aliphatic (e.g., alkyl or        alkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl)        substituents, and aromatic-, aliphatic-, and        alicyclic-substituted aromatic substituents, as well as cyclic        substituents wherein the ring is completed through another        portion of the molecule (e.g., two substituents together form a        ring);    -   substituted hydrocarbon substituents, that is, substituents        containing non-hydrocarbon groups which, in the context of this        invention, do not alter the predominantly hydrocarbon        substituent (e.g., halo (especially chloro and fluoro), hydroxy,        alkoxy, mercapto, alkylmercapto, nitro, nitroso, and sulfoxy);    -   hetero substituents, that is, substituents which, while having a        predominantly hydrocarbon character, in the context of this        invention, contain other than carbon in a ring or chain        otherwise composed of carbon atoms. Heteroatoms include sulfur,        oxygen, nitrogen, and encompass substituents as pyridyl, furyl,        thienyl and imidazolyl. In general, no more than two, preferably        no more than one, non-hydrocarbon substituent will be present        for every ten carbon atoms in the hydrocarbyl group; typically,        there will be no non-hydrocarbon substituents in the hydrocarbyl        group.

It is known that some of the materials described above may interact inthe final formulation, so that the components of the final formulationmay be different from those that are initially added. For instance,metal ions (of, e.g., a detergent) can migrate to other acidic oranionic sites of other molecules. The products formed thereby, includingthe products formed upon employing the composition of the presentinvention in its intended use, may not susceptible of easy description.Nevertheless, all such modifications and reaction products are includedwithin the scope of the present invention; the present inventionencompasses the composition prepared by admixing the componentsdescribed above.

EXAMPLES Example 1

A formulation is prepared containing 100 parts by weight of an API GroupIII base stock having a viscosity of 3.7-3.8 cSt at 100° C.; 2.55 partsborated succinimide dispersant based on polyisobutenylsuccinic anhydridereacted with polyethyleneamines, containing 1.9% B, 67% active chemicaland 33% diluent oil; 0.2 parts overbased calcium sulfonate detergentbased on a formaldehyde-coupled polypropylene-substituted sulfonic acid,300 Total Base Number (TBN), 58% active chemical and 42% diluent oil;0.2 parts overbased magnesium alkaryl sulfonate detergent, 400 TBN, 58%active chemical and 42% diluent oil; and 0.16 parts 85% phosphoric acid.The overbased detergents are commercial carbonated materials, which maycontain small amounts of dispersants and other conventional components.In addition, the formulation contains 0.05 parts dibutyl hydrogenphosphite, 0.03 parts of a commercial antifoam agent, 0.05 partsadditional diluent oil, and 10 parts dispersant viscosity modifier,based on a methacrylate copolymer with amine functionality (74 percentpolymer, 26 percent diluent oil).

Example 2

A formulation is prepared as in Example 1, except that the magnesiumdetergent is replaced by 0.19 parts of a similar borated magnesiumsulfonate detergent, 3.8% B, 295 TBN, 61% active chemical, 39% diluentoil; and the amount of the 85% phosphoric acid is reduced to 0.05 parts.Both of the formulations are tested and found to have a dynamicmetal-on-metal coefficient of friction of greater than 0.130 (500 mm/ssliding speed) as well as a plot of metal-on-metal coefficient offriction that exhibits a positive slope over the range of 20-1000 mm/s.

Example 3

A formulation is prepared as in Example 1, except that the magnesiumdetergent is replaced by 0.23 parts of an overbased magnesiumalkyl-substituted phenate, TBN 69, including 50% diluent oil, and thecalcium detergent is replaced by 0.19 parts of an overbased calciumalkyl-substituted salicylate, TBN 165, including 40% diluent oil. Theformulation exhibits a high dynamic metal-on-metal coefficient offriction.

Examples 4-11

To the formulation of Example 1 is added 0.5 parts by weight (activechemical basis) of each of the following materials, in turn:

(4) A Mannich condensation product of a branched alkyl-substitutedphenol, formaldehyde, and diethanolamine.

(5) A formaldehyde-coupled linear alkyl-substituted phenol.

(6) The condensation product of a linear alkyl-substituted succinicanhydride with diethanolamine.

(7) A polyisobutene substituted succinic anhydride

(8) A triphenyl thiophosphate

(9) A di(long chain alkyl) phosphite

(10) N-phenyl alpha-naphthylamine

(11) A sulfurized vegetable oil, optionally including also a sulfurizedolefin.

Examples 12-15

A formulation is prepared as in Example 1, except that the magnesiumdetergent and/or the calcium detergent are replaced in turn bycorresponding amounts of the following magnesium and/or calciumdetergents, respectively:

(12) An overbased calcium alkylphenate, sulfurized

(13) An overbased calcium sulfonate, borated

(14) An overbased magnesium alkylphenate

(15) An overbased magnesium alkylphenate and an overbased calcium saltof the reaction product of alkylphenol and glyoxylic acid.

Each of the documents referred to above is incorporated herein byreference. Except in the Examples, or where otherwise explicitlyindicated, all numerical quantities in this description specifyingamounts of materials, reaction conditions, molecular weights, number ofcarbon atoms, and the like, are to be understood as modified by the word“about.” Unless otherwise indicated, each chemical or compositionreferred to herein should be interpreted as being a commercial gradematerial which may contain the isomers, by-products, derivatives, andother such materials which are normally understood to be present in thecommercial grade. However, the amount of each chemical component ispresented exclusive of any solvent or diluent oil which may becustomarily present in the commercial material, unless otherwiseindicated. It is to be understood that the upper and lower amount,range, and ratio limits set forth herein may be independently combined.As used herein, the expression “consisting essentially of” permits theinclusion of substances which do not materially affect the basic andnovel characteristics of the composition under consideration.

1. A composition suitable for use as a lubricant for a transmission,comprising: (a) an oil of lubricating viscosity; (b) a dispersant; (c) acalcium detergent; (d) a magnesium detergent; and (e) an inorganicphosphorus compound; wherein at least one of (b), (c), and (d) isborated.
 2. The composition of claim 1 wherein the dispersant is aborated succinimide dispersant.
 3. The composition of claim 1 whereinthe dispersant is present in an amount of about 0.5 to about 6 percentby weight
 4. The composition of claim 1 wherein the dispersantcontributes about 50 to about 3000 parts per million by weight boron tothe composition.
 5. The composition of claim 1 wherein the calciumdetergent is an overbased calcium hydrocarbylbenzenesulfonate or anoverbased calcium hydrocarbylsalicylate.
 6. The composition of claim 1wherein the amount of the calcium detergent is about 0.025 to about 6weight percent.
 7. The composition of claim 1 wherein the magnesiumdetergent is an overbased magnesium hydrocarbylbenzenesulfonate or anoverbased magnesium hydrocarbylphenate.
 8. The composition of claim 1wherein the amount of the magnesium detergent is about 0.025 to about 6weight percent
 9. The composition of claim 1 wherein at least one of thecalcium detergent and the magnesium detergent is borated.
 10. Thecomposition of claim 1 containing about 130 to about 3300 parts permillion by weight boron.
 11. The composition of claim 1 wherein theinorganic phosphorus compound is phosphoric acid or phosphorous acid.12. The composition of claim 1 wherein the amount of the inorganicphosphorous compound is about 0.005 to about 0.3 percent by weight. 13.The composition of claim 1 further comprising (f) about 0.01 to about 6weight percent of an organic phosphorus ester.
 14. A concentratecomprising the composition of claim 1 wherein the amount of the oil oflubricating viscosity is about 10% to about 50% by weight.
 15. A methodfor lubricating a transmission, comprising supplying to saidtransmission the composition of claim 1.